This invention relates to methods and complexes for forming metal-containing films, such as metal or metal alloy films, particularly during the manufacture of semiconductor structures. The complexes include a Group IIIA metal, and are particularly suitable for use in a chemical vapor deposition system.
Aluminum is one of the three primary materials used today in semiconductor structures, the other two being silicon and silicon dioxide. It is primarily used in thin films as an interconnect between the specific structures formed on semiconductor substrates or substrate assemblies. Aluminum has been an important material in the fabrication of semiconductor structures because of its high conductivity, low resistivity (2.7 xcexcxcexa9-cm), high adherence to silicon and silicon dioxide, and low stress. Its use is also expanding into other metallization applications. For example, it is being examined to replace tungsten in contacts or vias (i.e., very small openings located, for example, between surface conductive paths and or xe2x80x9cwiringxe2x80x9d and active devices on underlying layers), which are getting narrower and deeper, and harder to fill with metal.
Aluminum alloys are also used in semiconductor structures, including alloys of aluminum with copper, titanium, etc., and combinations thereof. The addition of small quantities (typically, about 0.1-4%) of other metals to aluminum improves the electromigration resistance and reduces the propensity of aluminum thin-films to form hillocks (i.e., protrusions on the aluminum film surface). Such films, however, have increased resistivity over that of pure aluminum films.
In some applications, aluminum films are deposited using sputtering techniques; however, sputtered aluminum is not effective at filling contacts or vias because of shoulders or overhangs that form at the contact openings. These overhangs can lead to the formation of keyhole-shaped voids. Various collimation techniques help reduce this problem, but typically not enough to enable complete filling of very small geometries (e.g., less than about 0.5 xcexcm). Therefore, it is desirable to use chemical vapor deposition (CVD) to form aluminum and aluminum alloy films.
Dimethylaluminum hydride has emerged as one of the preferred materials for aluminum metallization by CVD. A serious problem with this material, however, is its pyrophoricity. This problem has been addressed to some degree by the addition of amines to the compound to act as stabilizing Lewis base donors to the aluminum center. However, such precursor compounds are still pyrophoric, albeit to a lesser extent. An additional complicating factor is introduced into the vapor pressure behavior of the precursor as a result of dissociation of the amine. Thus, there is a continuing need for methods and precursors for the deposition of aluminum and aluminum alloy films, as well as other Group IIIA metal or metal alloy films, on semiconductor structures, particularly using vapor deposition processes.
The present invention provides complexes and methods for forming metal-containing films, particularly Group IIIA metal-containing films on substrates, such as semiconductor substrates or substrate assemblies, during the manufacture of semiconductor structures. The method involves forming a metal-containing film using a Group IIIA metal complex, preferably a Group IIIA metal hydride complex. The metal-containing film can be used in various metallization layers, particularly in multilevel interconnects, in an integrated circuit structure.
The metal-containing film can be a single Group IIIA metal, or a metal alloy containing a mixture of Group IIIA metals or a Group IIIA metal and one or more metals or metalloids from other groups in the Periodic Chart, such as copper, silicon, titanium, vanadium, niobium, molybdenum, tungsten, scandium, etc. Furthermore, for certain preferred embodiments, the metal-containing film can be a nitride, phosphide, arsenide, stibnide, or combination thereof. That is, the metal-containing film can be a Group IIIA-VA (e.g., GaAs) semiconductor layer.
Thus, in the context of the present invention, the term xe2x80x9cGroup IIIA metal-containing filmxe2x80x9d or simply xe2x80x9cmetal-containing filmxe2x80x9d includes, for example, relatively pure films of aluminum, gallium, or indium, alloys of aluminum, gallium, and/or indium with or without other non-pnicogen metals or metalloids, as well as complexes of these metals and alloys with Group VA elements (N, P, As, Sb) or mixtures thereof. The terms xe2x80x9csingle Group IIIA metal filmxe2x80x9d or xe2x80x9cGroup IIIA metal filmxe2x80x9d refer to films of aluminum, gallium, or indium, for example. The terms xe2x80x9cGroup IIIA metal alloy filmxe2x80x9d or xe2x80x9cmetal alloy filmxe2x80x9d refer to films of aluminum, gallium, and/or indium alloys with or without other metals or metalloids, for example. That is, if there are no metals or metalloids from groups in the Periodic Chart other than Group IIIA, the alloy films contain combinations of aluminum, gallium, and indium. Preferably, the metal alloy films do not contain Group VA metals or metalloids (i.e., pnicogens).
One preferred method of the present invention involves forming a film on a substrate, such as a semiconductor substrate or substrate assembly during the manufacture of a semiconductor structure, by: providing a substrate (preferably, a semiconductor substrate or substrate assembly); providing a precursor comprising one or more complexes of the formulas: 
and 
wherein: M is a Group IIIA metal; each R1, R2, R3, R4, and R5 is independently H or an organic group; x=1 to 3; n=1 to 6 preferably, n=3 or 4); y=1 when x=1 and y=3-x when x=2 or 3; and z=3-xxe2x80x94y; and forming a metal-containing film from the precursor on a surface of the substrate (preferably, the semiconductor substrate or substrate assembly). The dashed arrow indicates that a nitrogen to metal dative bond may or may not be present. The metal-containing film is a Group IIIA metal film or a Group IIIA metal alloy film. Using such methods, the complexes of Formulas I and II are converted in some manner (e.g., decomposed thermally) and deposited on a surface to form a Group IIIA metal-containing film. Thus, the film is not simply a film of the complex of Formulas I or II.
The complexes of Formulas I and II are neutral complexes and may be liquids or solids at room temperature. If they are solids, they are preferably sufficiently soluble in an organic solvent to allow for vaporization by flash vaporization, bubbling, microdroplet formation, etc. However, these complexes can also be vaporized or sublimed from the solid state using known chemical vapor deposition techniques.
Another method of the present invention involves forming a film on a substrate, such as a semiconductor substrate or substrate assembly during the manufacture of a semiconductor structure, by: providing a substrate (preferably, a semiconductor substrate or substrate assembly); providing a precursor comprising one or more precursor hydride complexes of Formulas I and II above, wherein: M is a Group IIIA metal; each R1, R2, R3, R4, and R5 is independently H or an organic group with the proviso that at least one of R3 and R4 is H, and R5 is H; x=1 to 3; n=1 to 6; y=1 when x=1 and y=3-x when x=2 or 3; and z=3-xxe2x80x94y; and forming a metal-containing film from the precursor on a surface of the substrate.
Yet another method of forming a metal-containing film on a substrate, such as a semiconductor substrate or substrate assembly during the manufacture of a semiconductor structure, by: providing a substrate (preferably, a semiconductor substrate or substrate assembly); providing a liquid precursor comprising one or more precursor hydride complexes of Formulas I and II above, wherein: M is a Group IIIA metal; each R1, R2, R3, R4, and R5 group is independently H or a (C1-C30)organic group, with the proviso that at least one of R3 and R4 is H in Formula I and R5 is H in Formula II; x=1 to 3; n=1 to 6; y=1 when x=1 and y=3-x when x=2 or 3; and z=3-xxe2x80x94y; vaporizing the liquid precursor to form vaporized precursor; and directing the vaporized precursor toward the substrate to form a metal-containing film on a surface of the substrate.
Thus, preferred embodiments of the methods of the present invention involve the use of one or more chemical vapor deposition techniques, although this is not necessarily required. That is, for certain embodiments, sputtering, spin-on coating, etc., can be used.
The methods of the present invention are particularly well suited for forming films on a surface of a semiconductor substrate or substrate assembly, such as a silicon wafer, with or without layers or structures formed thereon, used in forming integrated circuits. It is to be understood that the method of the present invention is not limited to deposition on silicon wafers; rather, other types of wafers (e.g., gallium arsenide wafer, etc.) can be used as well. Also, the methods of the present invention can be used in silicon-on-insulator technology. Furthermore, substrates other than semiconductor substrates or substrate assemblies can be used in the method of the present invention. These include, for example, fibers, wires, etc. If the substrate is a semiconductor substrate or substrate assembly, the films can be formed directly on the lowest semiconductor surface of the substrate, or they can be formed on any of a variety of the layers (i.e., surfaces) as in a patterned wafer, for example. Thus, the term xe2x80x9csemiconductor substratexe2x80x9d refers to the base semiconductor layer, e.g., the lowest layer of silicon material in a wafer or a silicon layer deposited on another material such as silicon on sapphire. The term xe2x80x9csemiconductor substrate assemblyxe2x80x9d refers to the semiconductor substrate having one or more layers or structures formed thereon. The compounds of Formulas I and II incorporate features that make them selective for silicon over silicon dioxide.
Also, the present invention provides a hydride complex of Formulas I or II wherein: M is a Group IIIA metal (preferably Al, Ga, In); each R1, R2, R3, R4, and R5 group is independently H or an organic group, with the proviso that at least one of R3 and R4 is H in Formula I and R5 is H in Formula II; x=1 to 3; n=1 to 6; y=1 when x=1 and y=3-x when x=2 or 3; and z=3-xxe2x80x94y.
A chemical vapor deposition system is also provided. The system includes a deposition chamber having a substrate positioned therein; a vessel containing a precursor comprising one or more complexes of Formulas I and II wherein M is a Group IIIA metal, each R1, R2, R3, R4, and R5 group is independently H or an organic group, x=1 to 3, n=1 to 6, y=1 when x=1 and y=3-x when x=2 or 3, and z=3-xxe2x80x94y; and a source of an inert carrier gas for transferring the complexes to the chemical vapor deposition chamber.